Technical Field
The present invention relates to high mobility channel devices, and more particularly to devices and methods for forming complementary metal oxide semiconductor (CMOS) devices without extension doping below gate structures.
Description of the Related Art
High mobility channel devices are useful in high speed applications, such as, e.g., communications and high speed computing. Due to their high speed operation, defects in high mobility devices have a larger impact on device function. To ensure proper operation, in one example, low temperature processes (less than 650 degrees C.) need to be employed due to thermal instability of channel materials. The low temperature regimes limit dopant diffusion to/from the channel. In addition, extension dopant processes to extend the channel under spacer structures employ higher temperature implantation steps that may cause collateral damage and undesirable diffusion. Further, if source/drain (S/D) junctions are formed with an in-situ doped epitaxial process, it is difficult to link the S/D region to the channel due to the presence of spacer structures, which protect the gate during the epitaxial process.